Method for reducing engine oil dilution

Abstract

Various systems and methods are described for reducing engine oil dilution in a boosted engine. One method comprises, when engine oil dilution is higher than a first threshold and engine oil temperature is below a temperature threshold, adjusting a position of an air induction system (AIS) throttle, generating a vacuum, and providing the vacuum to a crankcase of the boosted engine to enhance fuel evaporation from engine oil. The providing of vacuum may be discontinued when engine oil dilution is lower than the first threshold and/or when engine oil temperature rises above the temperature threshold.

The invention claimed is: 
     
       1. A system, comprising:
 an engine with an intake passage; 
 a turbocharger with an intake compressor; 
 an air induction system (AIS) throttle positioned in the intake passage upstream of the intake compressor; 
 a crankcase; and 
 a controller with computer readable instructions stored in non-transitory memory for: 
 during a first condition,
 decreasing an opening of the AIS throttle to reduce pressure in the intake passage; and 
 applying the reduced pressure to the crankcase to enhance fuel evaporation; and during a second condition, 
 increasing the opening of the AIS throttle; and 
 disabling the applying of reduced pressure to the crankcase. 
 
 
     
     
       2. The system of  claim 1 , wherein the first condition includes engine oil dilution being greater than a first threshold, and engine oil temperature being lower than a second threshold. 
     
     
       3. The system of  claim 2 , wherein the second condition includes one or more of engine oil dilution being lower than the first threshold, engine oil temperature being greater than the second threshold for a duration longer than a threshold duration, and a level of pressure in the crankcase being lower than a third threshold. 
     
     
       4. The system of  claim 1 , wherein the controller includes further instructions for adjusting one or more of fuel injection amount and injection timing in response to receiving fuel vapors from the crankcase. 
     
     
       5. The system of  claim 1 , wherein fuel vapors from crankcase are delivered to the intake passage via a push port. 
     
     
       6. A method for a boosted engine comprising:
 when engine oil dilution is higher than a first threshold and engine oil temperature is below a temperature threshold,
 adjusting a position of an air induction system (AIS) throttle; 
 generating a vacuum; and 
 applying the vacuum to a crankcase to enhance fuel evaporation from engine oil. 
 
 
     
     
       7. The method of  claim 6 , wherein the adjusting includes adjusting the AIS throttle to a more closed position. 
     
     
       8. The method of  claim 7 , wherein the applying of vacuum is disabled when engine oil dilution is lower than the first threshold. 
     
     
       9. The method of  claim 8 , wherein the applying of vacuum is disabled when engine oil temperature is higher than the temperature threshold. 
     
     
       10. The method of  claim 9 , further comprising adjusting the position of the AIS throttle responsive to a change in an engine operating parameter. 
     
     
       11. The method of  claim 10 , wherein the engine operating parameter is engine torque. 
     
     
       12. The method of  claim 11 , wherein the position of the AIS throttle is adjusted to a more open position in response to an increase in engine torque. 
     
     
       13. The method of  claim 9 , wherein the applying of vacuum is disabled in response to a level of pressure in crankcase decreasing below a pressure threshold. 
     
     
       14. The method of  claim 6 , further comprising adjusting one or more of a fuel injection amount and fuel injection timing based on fuel vapors received from the crankcase to maintain engine combustion at or around stoichiometry. 
     
     
       15. The method of  claim 14 , wherein the fuel injection amount is decreased in response to an increase in fuel vapors received from the crankcase. 
     
     
       16. The method of  claim 6 , wherein engine oil dilution is detected via an intake oxygen sensor. 
     
     
       17. A method for a boosted engine, comprising:
 when engine oil temperature is lower than a first threshold,
 decreasing an opening of an air induction system (AIS) throttle if an engine oil dilution is greater than a second threshold; and 
 increasing the opening of the AIS throttle responsive to a change in an engine operating parameter. 
 
 
     
     
       18. The method of  claim 17 , wherein the engine operating parameter is engine torque, and wherein the opening of the AIS throttle is increased in response to an increase in engine torque. 
     
     
       19. The method of  claim 17 , further comprising increasing the opening of the AIS throttle responsive to an increase in engine oil temperature above the first threshold for a duration longer than a threshold duration. 
     
     
       20. The method of  claim 17 , further comprising opening the AIS throttle responsive to the engine oil dilution decreasing below the second threshold.